Rainfall

January 2007 saw a marked east/west distribution of rainfall. Above average and very much above average rainfall totals were recorded in western parts of the state, while below average and very much below average rainfall totals were recorded in eastern parts. Much of central NSW recorded close to average rainfall for January. This distribution can be attributed to a persistent monsoonal low that moved from southern Northern Territory into southwest Queensland, which was combined with anomalous northwesterly flow across the state. This enhanced moisture in western NSW, but resulted in drier conditions along the coast, which usually experiences moist southeasterly flows at this time of the year.

The statewide average rainfall for January was 41.9 mm, less than the historical average1 of 68.0 mm. The Murray Darling Basin recorded an average of 46.2 mm compared to the historical average of 57.4 mm.

Temperature

Maximum temperatures were above average to very much above average across the east of the state, with northern parts of the Southern Tablelands experiencing the highest maximum temperatures on record. Parts of the far northwest were the only areas to experience below average maximum temperatures. The statewide average maximum temperature was 1.4°C above the historical January average1 of 31.6°C, making it the tenth consecutive January with above average maximum temperatures.

Minimum temperatures were above average across most of the state except for the coast and adjacent ranges north of Sydney, which were slightly below average. The statewide average minimum temperature was 1.0°C above the historical January average of 17.7°C.

Other phenomena

Unusually cool water temperatures were experienced off the NSW coast during January. Some recorded temperatures were cooler than those typically experienced in winter. The cool water was caused by a period of prolonged NE winds circulating around a large, slow moving high pressure system in the Tasman Sea early in the month. This drew the surface water away from the coast, causing colder water in the deeper layers to upwell.

Notes

This statement has been prepared based on information available at
2 pm on Thursday, 1st February 2007.
Some checks have been made on the data, but it is possible that results will change
as new information becomes available.

A note about deciles: Deciles are used to give an element (in this case rainfall or temperature) a ranking. Deciles are calculated by arranging the totals in ascending order (from lowest to highest) then splitting them into 10 equal groups (thus the groups are called deciles). The first group would be in decile range one, the second group in decile range two, etc up to the highest annual totals (highest 10 per cent) being in decile range 10.

1Averages: Averages are based on the period 1961 to 1990 which is a convention of the World Meteorological Organisation

Normals are long-term averages based on observations from
all available years of record, which vary widely from site to site.
They are not shown for sites with less than 20 years of record for temperature and less than 30 years of record for rainfall, as they cannot then be calculated reliably.